This invention relates to pressurized fluid flow lines and more particularly to apparatus for the injection or retrieval of plugs or balls, such as solid rubber spheres or cylinder wax slugs, which items are introduced into a pressurized fluid line for such purposes as cleaning out pockets of liquid or separating different products within the line.
In pressurized fluid lines, such as gas and oil pipelines, clogging or restrictions may occur within the pipeline as a result of deposits and the like, thus affecting the flow through the line. In order to clean out such deposits or pockets of foreign matter, it is conventional practice to insert balls or plugs into the line which are driven forward by the line fluid pressure and push the deposits or pockets of foreign material forward in the line to a trap area or reservoir.
Further, it is conventional to use balls or plugs to separate different products within a line or to distinguish quantities of products within a line.
It is desirable that the flow of pressurized fluid not be interrupted or restricted or, at least, that any interruption be minimized. Consequently, it is desirable that the line flow not be stopped or shut off during the process of introducing or retrieving a ball or plug. Inasmuch as the fluid within a line may be under significant pressure, leakage and spillage of the fluid product will often occur during the injection or retrieval operation. As illustrated in U.S. Pat. No. 3,146,477, seals may be arranged within the injection valve housing to limit seepage directly from the pressurized line fluid when the valve is in a ball loading position or in a position for injecting the ball into the fluid line. However, fluid will find its way into the loading chamber area during operation of the valve and spillage of this trapped fluid may thus occur as balls or plugs are loaded or unloaded even though the pressurized line fluid is sealed off during that procedure.
The seals utilized in an injector valve may be subjected to the high pressure of the fluid line as well as to unpressurized port or chamber areas. The pressure differentials to which the seals are exposed can cause the seals to be pinched and cut during the operation of the valve as the they are urged toward low pressure areas. Occasionally, such seals may be caused to blowout when sudden exposure to open and unpressurized chamber or port areas occur.
The wear to which the seals of an injector valve are subjected can result in leakage of fluid directly from the pressurized fluid line through the valve and increased maintenance and attention for the valve. Prior injector valve devices have tried to overcome the problem of seal wear and blowout potential by use of dovetail type grooves for containing the seals in the valve housing and piston. The dovetail groove formation tends to structurally retain the seal in its position within the groove despite the pressure differential acting across the seal. However, such grooves are more expensive and difficult to machine into the valve components.